The screen I have on my car for the rear view camera supports only composite signal, so that would not work on the Oric without some converter, but internally they probably all get converted to RGB, so I would not be surprised if some of these screens can get direct RGB input.

Most probably your device has only AV-input - this is CVBS or as Dbug already said input for composite video signal.
You can use external RGB to Composite converter (simply search e-bay), relatively not cheap solution but it works.
Else, if you like hardware hacking, there are 2 possibilities (atleast ):
- open your Oric and get composite signal before the UHF modulator, additionally you need simple 1 transistor inverter-amplifier to adjust signal level - this worked for me - I use portable 7-inch DVD player with the same resolution 480 x 234 pixels.
- hack your device - theoretically there is chance to connect RGB+Synchro signals from Oric directly (or with few resistors) to somewhere on the TV's PCB. For this you will need the service manual and data-sheets for your device.

If there is interest I can post the "know-how" how to convert broken 7-inch DVD player for 3EUR into portable monitor with Composite, S-Video and RGB inputs.

Here are 'schematics'.
This is part of the well-known Oric schematic showing where to get AV signal:

And this is the one-transistor stage:

AV-cvt.png (2.95 KiB) Viewed 12969 times

As you can see in first picture I removed R15 and RV1. They can remain, but than R0* (in second picture) should be used.

As conclusion I can say that the quality is not 'the best' but it's fully acceptable.
Some scanlines are missing, so text is bit hard to read, but in general for demo purposes and 'mobile gaming' is OK!